The present invention relates to fuel system valves and in particular fuel vapor release valves for use with venting passageways and tanks in a vehicle fuel system. Specifically, the fuel vapor release valve of the present invention can be utilized as a rollover valve for the prevention of fuel spillage in the case of tilting of the vehicle beyond a specified longitudinal axis. The present invention can also be utilized as a liquid vapor discriminator valve for use in venting fuel lines and fuel filler necks and tanks.
Fuel vapor release valves are commonly incorporated as rollover valves in vehicle fuel systems for the purposes of releasing vapor pressure buildup in the fuel tank and filler necks. Vapor pressure release valves commonly will vent fuel vapors to a charcoal or carbon canister for storage until the vapors can be forwarded to the engine for combustion. The priority objective for most vapor release valves is to allow the venting of fuel vapor from a pressurized vessel while preventing any liquid fuel from escaping. Venting is most commonly conducted through an orifice to provide a controlled flow rate. Thus, vapor release valves or rollover valves must be designed to close their vapor outlets or ports during extreme tilting or rollover of the vehicle in order to prevent spillage of liquid fuel through the vapor outlet and thereby assist in preventing the potential for fires.
Vehicle fuel system tanks are allowed a maximum operative vapor pressure of fifteen kilopascals (kPa) during normal operating conditions. Rollover valves are designed to facilitate the maintenance of the vapor pressure within a vehicle fuel system at a predesired level. If the rollover valve were to close, there is a commonly encountered problem in reopening the closed rollover valve because the pressurized fuel vapor existing within the fuel system applies forces against the valve seat which must be overcome to reopen the valve. This condition is commonly called "corking". In a corking situation, the pressure in the fuel tank exerts enough force over the area of the valve orifice that the valve cannot easily reopen upon the return of the vehicle to normal operating conditions. As a result, most rollover valves are designed to have a small orifice, generally in the range of 1 to 2 millimeters in diameter. The forces applied by the fuel system vapor pressure against the small area of the outlet closure can then be easily overcome by the proper sizing and weighting of the float. However, in fuel systems where high vapor pressure occurs and where high vapor flow rates are required, a rollover valve having a small orifice is inadequate to fully relieve the vapor pressure.
Therefore, it is an object of this invention to provide a high volume fuel vapor release valve having a large diameter outlet or port capable of venting all fuel vapor generated in the tank during normal operating conditions.
A further object of the invention is to provide a fuel vapor release valve which will regularly vent all vapor generated in the fuel tank and reduce the tank pressure to a nominal or atmospheric pressure during normal operating conditions.
Yet another object of the present invention is to provide a fuel vapor release valve which will vent a high flow rate of vapor during operating conditions, close in the presence of liquid fuel and during vehicle tilting, and yet require a low force to reopen the closed valve.